COD, I realize I am showing up very late to this party, but I did want to point out that ASTM F2170 requires the space to be acclimated (HVAC on) prior to testing for relative humidity. This may have been skewing your data.

(04-18-2011, 12:26 PM)T_Schneider Wrote: COD, I realize I am showing up very late to this party, but I did want to point out that ASTM F2170 requires the space to be acclimated (HVAC on) prior to testing for relative humidity. This may have been skewing your data.

Regards,

T. Schneider
ARDEX Engineered Cements

Technically nowhere in the ASTM does it say the space must have the HVAC on.

We wouldn't want testers thinking they cannot conduct accurate RH testing just because the HVAC is not on. In 99% of all the hospitals I work in, the HVAC is not commissioned until a few days before the building is turned over.

OK, I stand corrected, it does not specifically mention HVAC, but it does say that the concrete must be "at service temperature" and that the air space above the concrete "shall be at service temperature and service relative humidity." Both of these are stipulated "for at least 48 hours before making relative humidity measurements in the concrete slab." IMO, HVAC is strongly implied by this, unless you happen to be having a string of lovely, 72-degree and 0% humidity days. If that happens often where you are, tell me where you live - I'm moving!

Well let's consider service temperature.... ASTM F1869 has the same wording yet also adds that temperatures between 65F and 85F and Rh in the 40% to 60% range is acceptable. I think we can all agree that RH probes are less susceptible to temperature fluctuations than MVER testing equipment.

But I'll make my point with this: Most job sites will be under temporary conditioning when new construction is being conducted. This temporary heating and cooling can and does provide adequate testing climates for RH testing. Limiting testing to a time when HVAC is active is not practical on commercial jobs.

(04-18-2011, 01:20 PM)T_Schneider Wrote: OK, I stand corrected, it does not specifically mention HVAC, but it does say that the concrete must be "at service temperature" and that the air space above the concrete "shall be at service temperature and service relative humidity." Both of these are stipulated "for at least 48 hours before making relative humidity measurements in the concrete slab." IMO, HVAC is strongly implied by this, unless you happen to be having a string of lovely, 72-degree and 0% humidity days. If that happens often where you are, tell me where you live - I'm moving!

I just had a GC in Los Angeles tell me they can't get the building acclimated because they can't get heat on until they get the occupancy permit and cant get occupancy permit until flooring is done ....